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US 5652312 A Zusammenfassung Polyestercarbonates, particularly those containing aliphatic dicarboxylic acid-derived structural units, are redistributed by heating in the presence of a carbonate redistribution catalyst, and, optionally, a diaryl carbonate. The redistribution products have weight average molecular weights different from, and typically lower than, the initial molecular weight. Ansprüche 1. A method for the redistribution of an organic polyestercarbonate composition comprising heating an initial linear or branched organic polyestercarbonate composition having a weight average molecular weight from 500 to 200,000 and having a major proportion of carbonate structural units and a minor proportion of units derived from at least one dihydroxyaromatic compound and at least one aliphatic dicarboxylic acid containing about 4-20 carbon atoms, at a temperature in the range of about 180 redistribution catalyst in the amount of about 15-1000 ppm based on initial polyestercarbonate and in the absence of branching agents, thus forming a redistributed polyestercarbonate composition having a weight average molecular weight which is different from the initial molecular weight. 2. A method according to claim 1 wherein the carbonate structural units in the polyestercarbonate are aromatic. 3. A method according to claim 2 wherein the carbonate structural units are bisphenol A carbonate units. 4. A method according to claim 2 wherein the aliphatic acid is adipic acid. 5. A method according to claim 2 wherein the aliphatic acid is 1,12-dodecanedioic acid. 6. A method according to claim 2 wherein the catalyst is a tetraalkylammonium base. 7. A method according to claim 6 wherein the catalyst is a c.sub.1-16 tetraalkylammonium hydroxide. 8. A method according to claim 6 wherein the catalyst is a C.sub.1-16 tetraalkylammonium acetate. 9. A method according to claim 6 wherein the amount of catalyst is about 15-1000 ppm based on polyestercarbonate. 10. A method for the redistribution of an organic polyestercarbonate composition comprising heating an initial linear or branched organic polyestercarbonate composition having a weight average molecular weight from 500 to 200,000 and having a major proportion of carbonate structural units and a minor proportion of units derived from at least one dihydroxyaromatic compound and at least one aliphatic dicarboxylic acid containing about 4-20 carbon atoms, at a temperature in the range of about 180 redistribution catalyst in the amount of about 15-1000 ppm based on initial polyestercarbonate and a diaryl carbonate and in the absence of branching agents, thus forming a redistributed polyestercarbonate composition having a weight average molecular weight which is different from the initial molecular weight. 11. A method according to claim 11 wherein the carbonate structural units are bisphenol A carbonate units. 12. A method according to claim 10 wherein the aliphatic acid is adipic acid. 13. A method according to claim 10 wherein the aliphatic acid is 1,12-dodecanedioic acid. 14. A method according to claim 10 wherein the catalyst is a tetraalkylammonium base. 15. A method according to claim 14 wherein the amount of catalyst is about 15-1000 ppm based on polyestercarbonate. 16. A method according to claim 10 wherein the amount of diaryl carbonate is up to about 1.5% by weight based on polyestercarbonate. 17. A method according to claim 16 wherein the diarylcarbonate is diphenyl carbonate. 18. A method according to claim 1 which is conducted in an extruder. Beschreibung The following examples are illustrative of the method of this invention. Molecular weights were determined by gel permeation chromatography relative to polystyrene. The polyestercarbonates employed were bisphenol A polyestercarbonates incorporating 9% by weight adipic acid (AA) or 1,12-dodecanedioic acid (DDDA) units and having weight average molecular weights in the range of about 55.000-60,000. Samples of 1 kg. of polyestercarbonate and various proportions of tetraethylammonium acetate (TEAA) and (in Examples 4 and 8) diphenyl carbonate (DPC) were prepared by dry blending in a Henschel mixer. The blends were extruded on a twin screw extruder with vacuum venting, at temperatures in the range of 180 weights of the redistributed products, and in certain cases their dispersivities and hydroxy end group concentrations, were determined and are listed in the following table, in comparison with two controls in which no TEAA was employed and in which the molecular weights were therefore substantially those of the starting polyestercarbonates.
______________________________________ Hydroxy Acid TEAA, DPC, end groupExample units ppm wt. % Mw Mw/Mn conc., ppm______________________________________Control 1 AA -- -- 55,400 -- --1 AA 100 -- 50,800 -- --2 AA 200 -- 48,400 -- --3 AA 300 -- 44,0004 AA 300 0.5 39,700 -- --Control 2 DDDA -- -- 56,900 2.79 505 DDDA 100 -- 54,600 2.63 2206 DDDA 200 51,000 2.48 2407 DDDA 300 -- 46,800 2.45 3608 DDDA 300 0.5 39,500 2.48 420______________________________________ It will be seen that polyestercarbonates of various molecular weights may be produced by the method of the invention. Analysis for adipic acid units performed on Control 1 and the product of Example 3 in each case showed that the redistributed product still contained 100% of the original adipic acid units, demonstrating that degradation only of polycarbonate units occurred during redistribution. Patentzitate
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